A campaign by Palestinian activists demanding the UK issue a formal apology for supporting the idea of a Jewish state in the Middle East almost a century ago is gaining momentum after the launch of a new parliamentary petition.

Liberal Democrat peer Baroness Jenny Tonge hosted the launch at the House of Lords last Tuesday, where the plight of the Palestinian people was blamed on the legacy of the Balfour Declaration and wider British colonialism in the region.

The activists, backed by the Palestinian diplomatic mission in the UK, intend to push the British government in the run-up to the document’s centennial in November 2017. If the petition – currently pending approval – reaches 100,000 signatures, parliament will have to consider debating the subject.

The Balfour Declaration was a letter from British Foreign Secretary Arthur James Balfour to Lord Rothschild – head of the Zionist Federation of Great Britain and Ireland – that promised support for the idea of a Jewish homeland in historical Palestine as long as the rights of existing non-Jewish communities were not “prejudiced.”

Shortly after the letter was published, the Ottoman Empire was defeated by allied powers in World War I and Britain established mandate rule in the territory of historic Palestine, previously ruled by the Ottomans.

Last Tuesday’s event at Westminster proved controversial after a video surfaced showing one audience member saying Jews had “agitated” Adolf Hitler before the Holocaust, and compared Israel to Islamic State (IS, formerly ISIS, ISIL).

“Just as the so-called Jewish state in Palestine doesn’t come from Judaism, the Islamic State in Syria is nothing with Islam. It is a perversion of Islam just as Zionism is a perversion of Judaism,” the unidentified man said.

“If anybody is anti-Semitic, it’s Israelis themselves,” another audience member said, to applause.

Israel condemned what it called a “shameful” gathering, which “gave voice to racist tropes against Jews and Israelis alike.”

Tonge was criticised for not appearing to challenge the comments. She later said she did not hear the first man’s full “rant.” The Lib Dems decided to suspend Tonge, pending an investigation into the event.

"If anybody is antisemitic, it's the Israelis themselves"; panel applauds; hard to believe, but this happened this week at House of Lords pic.twitter.com/L8v4cARnK8

Palestinian Authority President Mahmoud Abbas also called on the UK to apologize for the Balfour Declaration while in New York last week.

“We ask Great Britain, as we approach 100 years since this infamous declaration, to draw the necessary lessons and to bear its historic, legal, political, material and moral responsibility for the consequences of this declaration, including an apology to the Palestinian people for the catastrophes, misery and injustice this declaration created and to act to rectify these disasters and remedy its consequences, including by the recognition of the state of Palestine,” Abbas told UN delegates.

“This is the least Great Britain can do.”

In a statement sent to Al Jazeera, a British Foreign and Commonwealth Office spokesperson said the government would not apologize for the 100-year-old document, but recognized it was a sensitive subject for many.

“The Balfour Declaration was a historic statement and one that the UK Government will not be apologising for… We are focused on encouraging the Israelis and Palestinians to take steps which bring them closer to peace,” the FCO said.